Asparagine endopeptidase protects podocytes in adriamycin-induced nephropathy by regulating actin dynamics through cleaving transgelin.

Focal segmental glomerulosclerosis (FSGS) is the most common glomerular disorder causing end-stage renal diseases worldwide. Central to the pathogenesis of FSGS is podocyte dysfunction, which is induced by diverse insults. However, the mechanism governing podocyte injury and repair remains largely unexplored. Asparagine endopeptidase (AEP), a lysosomal protease, regulates substrates by residue-specific cleavage or degradation. We identified the increased AEP expression in the primary proteinuria model which was induced by adriamycin (ADR) to mimic human FSGS. In vivo, global AEP knockout mice manifested increased injury-susceptibility of podocytes in ADR-induced nephropathy (ADRN). Podocyte-specific AEP knockout mice exhibited much more severe glomerular lesions and podocyte injury after ADR injection. In contrast, podocyte-specific augmentation of AEP in mice protected against ADRN. In vitro, knockdown and overexpression of AEP in human podocytes revealed the cytoprotection of AEP as a cytoskeleton regulator. Furthermore, transgelin, an actin-binding protein regulating actin dynamics, was cleaved by AEP, and, as a result, removed its actin-binding regulatory domain. The truncated transgelin regulated podocyte actin dynamics and repressed podocyte hypermotility, compared to the native full-length transgelin. Together, our data reveal a link between lysosomal protease AEP and podocyte cytoskeletal homeostasis, which suggests a potential therapeutic role for AEP in proteinuria disease.

UCP1 alleviates renal interstitial fibrosis progression through oxidative stress pathway mediated by SIRT3 protein stability.

BACKGROUND: Renal interstitial fibrosis is a common pathway for the progressive development of chronic renal diseases (CKD) with different etiology, and is the main pathological basis leading to end-stage renal disease. Although the current research on renal interstitial fibrosis is gradually deepening, the diagnosis and treatment methods are still very lacking. Uncoupling protein 1 (UCP1) is a nuclear encoded protein in mitochondria inner membrane and plays an important role in regulating energy metabolism and mitochondrial homeostasis. However, the biological significance of UCP1 and potential regulatory mechanisms in the development of CKD remain unclear. METHODS: Unilateral ureteral obstruction (UUO) model was used to construct the animal model of renal fibrosis, and TGF-ß1 stimulation of HK2 cells was used to construct the vitro model of renal fibrosis. UCP1 expression was detected by Western blot, immunoblot analysis and immunohistochemistry. UCP1 was upregulated by UCP1 overexpressing lentivirus and UCP1 agonist CL316243. Western blot and immunofluorescence were used to detect epithelial mesenchymal transition (EMT)-related markers, such as collagen I, fibronectin, antioxidant enzyme SOD2 and CAT. Reactive oxygen species (ROS) production was detected by ROS detection kit. SIRT3 knockdown was performed by siRNA. RESULTS: This study presents that UCP1 is significantly downregulated in patients with renal fibrosis and UUO model. Further studies discover that UCP1 overexpression and CL316243 treatments (UCP1 agonists) reversed EMT and extracellular matrix (ECM) accumulation in renal fibrosis models in vivo and in vitro. Simultaneously, UCP1 reduced the ROS production by increasing the stability of SIRT3. When SIRT3 was knocked down, the production of ROS decreased. CONCLUSIONS: Elevating the expression of UCP1 can inhibit the occurrence of oxidative stress by stabilizing SIRT3, thereby reducing EMT and ECM accumulation, and ultimately alleviating renal interstitial fibrosis. It will provide new instructions and targets for the treatment of CKD.

The association of five polymorphisms with diabetic retinopathy in a Chinese population.

PURPOSE: To comprehend the etiology of diabetic retinopathy (DR), it is crucial to clarify the genetic susceptibility factors for DR. Previous studies have reported that five single nucleotide polymorphisms (SNPs), including rs9362054 (near the CEP162 gene), rs1990145 (MRPL19), rs10519765 (FMN1), rs237025 (SUMO4) and rs767649 (MIR155HG) were associated with DR. This study was conducted to elucidate the association between the five SNPs and DR in a Chinese Han population. METHODS: A total of 957 individuals with type 2 diabetes mellitus (T2DM) including diabetes mellitus without retinopathy (DNR = 478), nonproliferative DR (NPDR = 384) and proliferative (PDR = 95) were recruited in this study. SNPs were genotyped using the Mass ARRAY MALDI-TOF system. The genotype and allele frequencies were determined using χ2 tests. For genotype and allele risk, odds ratios (OR) and 95% confidence intervals (CI) were calculated. Four genetic models (homozygous, heterozygous, dominant, and recessive) were used to further investigate the link between the five SNPs and DR. RESULTS: There was a statistically significant difference of CEP162 rs9362054 between NPDR and DNR (P = .027, OR = 1.26, 95%CI = 1.03-1.54) and a significant association of SUMO4 rs237025 detected between PDR and DNR (P = .031, OR = 1.45, 95%CI = 1.03-2.02). The association of CEP162 rs9362054 was also observed under the dominant mode (P = .03, OR = 1.35, 95%CI = 1.03-1.77). The association of SUMO4 rs237025 was found under the heterozygous model (P = .03, OR = 1.68, 95%CI = 1.06-2.69) and the dominant model (P = .02, OR = 1.70, 95%CI = 1.08-2.67). No associations of the other three SNPs with NPDR and PDR were detected when compared with DNR under these genetic models. CONCLUSIONS: This study showed that rs9362054 and rs237025 were associated with NPDR and PDR when compared with DNR, suggesting that SUMO4 may be involved in the development of PDR, while CEP162 may be associated with NPDR.

The MAD2B-APC/C-MDM2 axis mediates acute kidney injury by modulating p53.

P53 is a master regulator modulating the progression of acute kidney injury (AKI). However, the mechanism underlying p53 regulation in AKI needs further investigation. Mitotic arrest deficient 2 like 2 (MAD2B) is a subunit of DNA polymerase ζ. Its role in AKI remains unclear. Here, we demonstrated that MAD2B acted as an endogenous suppressor of p53. MAD2B conditional knockout augmented the upregulation of p53 in kidneys suffering from cisplatin-induced AKI, therefore promoting the deterioration of renal function, G1 phase arrest and apoptosis of proximal tubular epithelial cells. Mechanistically, MAD2B deficiency activated the anaphase-promoting complex/cyclosome (APC/C), which is an inhibitor of the well-characterized p53-directed E3 ligase MDM2. The decreased MDM2 diminished the degradation of p53, resulting in the upregulation of p53. The APC/C antagonist proTAME ameliorated cisplatin-induced AKI and blocked MAD2B knockdown-induced p53 upregulation and reduced cell cycle arrest and apoptosis in tubular epithelial cells by upregulating MDM2. These results indicate that MAD2B is a novel target for inhibiting p53 and ameliorating AKI.

Cofilin promotes tau pathology in Alzheimer's disease.

The molecular mechanisms mediating the aggregation and transmission of tau in AD remain unclear. Here, we show that the actin-binding protein cofilin is cleaved by a cysteine protease asparagine endopeptidase (AEP) at N138 in the brains of patients with AD. The AEP-generated cofilin 1-138 fragment interacts with tau and promotes its aggregation. The mixed fibrils consisting of cofilin 1-138 and tau are more pathogenic to cells than pure tau fibrils. Furthermore, overexpression of cofilin 1-138 in the brain facilitates the propagation of pathological tau aggregates and promotes AD-like cognitive impairments in tau P301S mice. However, mice infected with adeno-associated viruses (AAVs) encoding an AEP-uncleavable cofilin mutant show attenuated tau pathology and cognitive impairments compared with mice injected with AAVs encoding wild-type cofilin. Together, these observations support the role of the cofilin 1-138 fragment in the aggregation and transmission of tau pathology during the onset and progression of AD.

HTRA1 rs11528744, BCRA1 rs9928736, and B3GLCT rs4381465 are associated with age-related macular degeneration in a Chinese population.

Purpose: Age-related macular degeneration (AMD) is a leading cause of vision loss. A Previous study based on the co-localization analysis of the genome-wide association study (GWAS) and eQTL genetic signals have reported that single nucleotide polymorphisms (SNPs), including rs760975, rs11528744, rs3761159, rs7212510, rs6965458, rs7559693, rs56108400, rs28495773, rs9928736, rs11777697, rs4381465 are associated with AMD in Americans. The aim of this study was to investigate the association of these SNPs in a Han Chinese population. Methods: There were 576 patients with wet AMD and 572 healthy controls collected in this study. All SNPs were genotyped by flight mass spectrum. Hardy-Weinberg equilibrium was applied to evaluate allele distributions for both AMD and control groups. The genotype and allele frequencies were evaluated using the χ2 tests. Odds ratio (OR) and 95% confidence intervals (95% CI) were calculated for the risk of genotype and allele. Results: Three of the 11 SNPs (rs11528744 in HTRA1, rs9928736 in BCRA1 and rs4381465 in B3GLCT) were found to be significantly associated with AMD in the allelic model (corrected p = 0.001, OR = 1.391, 95%CI = 1.179-1.640 for rs11528744; corrected p = 0.004, OR = 0.695, 95%CI = 0.544-0.888 for rs9928736; corrected p = 0.002, OR = 0.614, 95%CI = 0.448-0.841 for rs4381465). There were no differences for the remaining eight SNPs between AMD cases and healthy controls. Conclusion: Our results showed that HTRA1 rs11528744, BCRA1 rs9928736, and B3GLCT rs4381465 were associated with wet AMD, suggesting that HTRA1, BCRA1, and B3GLCT genes may be involved in the development of AMD.

[Association analysis of seven single nucleotide polymorphisms identified by genome-wide association study with age-related macular degeneration among ethnic Han Chinese population].

OBJECTIVE: To assess the association of 7 single nucleotide polymorphisms (SNPs) including rs13278062 (TNFRSF10A), rs3750846 (ARMS2-HTRA1), rs429358 (APOE), rs5817082 (CEPT), rs2043085 (LIPC), rs1626340 (TGFBR1), and rs8135665 (SLC16A8) identified through genome-wide association study (GWAS) with age-related macular degeneration (AMD) among ethnic Han Chinese from Sichuan, China. METHODS: A cohort of 576 AMD patients and 572 healthy controls were enrolled in a case-control study. The SNPs were genotyped by a Mass array MALDI-TOF System. On the premise that the genotype distribution of each SNP locus in both groups satisfied Hardy-Weinberg equilibrium, the genetic pattern was analyzed and the scores of allele and genotype frequencies ware compared. RESULTS: There was a significant association between TNFRSF10A rs13278062 and AMD under the heterozygous model (P = 0.000, OR = 1.529, 95%CI = 1.196-1.954) and the dominant model (P = 0.002, OR = 1.459, 95%CI = 1.154-1.865), suggesting that subjects carrying rs13278062GT and rs13278062TT + GT are more likely to develop the AMD, whereas no significant difference was observed for rs13278062 under other models. No association was detected with the other six SNPs and AMD under various genetic models. CONCLUSION: This case-control association study has indicated that TNFRSF10A rs13278062 is associated with AMD under the heterozygous and dominant models, suggesting that the TNFRSF10A variant may be involved in the development of AMD among ethnic Han Chinese population.

MAD2B promotes podocyte injury through regulating Numb-dependent Notch 1 pathway in diabetic nephropathy.

Rationale: Recent studies have demonstrated that the loss of podocyte is a critical event in diabetic nephropathy (DN). Previously, our group have found that the mitotic arrest deficient protein MAD2B was involved in high glucose (HG)-induced podocyte injury by regulating APC/C activity. However, the exact mechanism of MAD2B implicated in podocyte injury is still lacking. Methods: The experiments were conducted by using kidney tissues from streptozotocin (STZ) induced diabetic mice with or without podocyte-specific deletion of MAD2B and the cultured podocytes exposed to different treatments. Glomerular pathological injury was evaluated by periodic acid-Schiff staining and transmission electron microscopy. The endogenous interaction between MAD2B and Numb was discovered by yeast two-hybrid analysis and co-immunoprecipitation assay. The expressions of MAD2B, Numb and related pathway were detected by western blot, immunochemistry and immunofluorescence. Results: The present study revealed that MAD2B was upregulated in diabetic glomeruli and cultured podocytes under hyperglycemic conditions. Podocyte-specific deletion of MAD2B alleviated podocyte injury and renal function deterioration in mice of diabetic nephropathy. Afterwards, MAD2B was found to interact with Numb, which was downregulated in diabetic glomeruli and HG-stimulated cultured podocytes. Interestingly, MAD2B genetic deletion could partly reverse the decline of Numb in podocytes exposed to HG and in diabetic mice, and the expressions of Numb downstream molecules such as NICD and Hes-1 were decreased accordingly. In addition, overexpression of Numb ameliorated HG-induced podocyte injury. Conclusions: The present findings suggest that upregulated MAD2B expression contributes to Numb depletion and activation of Notch 1 signaling pathway, which ultimately leads to podocyte injury during DN progression.

Asparaginyl endopeptidase protects against podocyte injury in diabetic nephropathy through cleaving cofilin-1.

Podocyte injury and loss are critical events in diabetic nephropathy (DN); however, the underlying molecular mechanisms remain unclear. Here, we demonstrate that asparaginyl endopeptidase (AEP) protects against podocyte injury through modulating the dynamics of the cytoskeleton. AEP was highly upregulated in diabetic glomeruli and hyperglycemic stimuli treated-podocytes; however, AEP gene knockout and its compound inhibitor treatment accelerated DN in streptozotocin-induced diabetic mice, whereas specific induction of AEP in glomerular cells attenuated podocyte injury and renal function deterioration. In vitro, elevated AEP was involved in actin cytoskeleton maintenance and anti-apoptosis effects. Mechanistically, we found that AEP directly cleaved the actin-binding protein cofilin-1 after the asparagine 138 (N138) site. The protein levels of endogenous cofilin-1 1-138 fragments were upregulated in diabetic podocytes, consistent with the changes in AEP levels. Importantly, we found that cofilin-1 1-138 fragments were remarkably unphosphorylated than full-length cofilin-1, indicating the enhanced cytoskeleton maintenance activity of cofilin-1 1-138. Then we validated cofilin-1 1-138 could rescue podocytes from cytoskeleton disarrangement and injury in diabetic conditions. Taken together, our data suggest a protective role of elevated AEP in podocyte injury during DN progression through cleaving cofilin-1 to maintain podocyte cytoskeleton dynamics and defend damage.

Risk factors for the mortality of hemodialysis patients with COVID-19: A multicenter study from the overall hemodialysis population in Wuhan.

INTRODUCTION: Maintenance hemodialysis (MHD) patients are highly threatened in the novel coronavirus disease 2019 (COVID-19) pandemic, but evidence of risk factors for mortality in this population is still lacking. METHODS: We followed outcomes of the overall MHD population of Wuhan, including 7154 MHD patients from 65 hemodialysis centers, from January 1 to May 4, 2020. Among them, 130 were diagnosed with COVID-19. The demographic and clinical data of them were collected and compared between survivors and nonsurvivors. RESULTS: Compared to the corresponding period of last year, the all-cause mortality rate of the Wuhan MHD population significantly rose in February, and dropped down in March 2020. Of the 130 COVID-19 cases, 51 (39.2%) were deceased. Advanced age, decreased oxygen saturation, low diastolic blood pressure (DBP) on admission, and complications including acute cardiac injury (HR 5.03 [95% CI 2.21-11.14], p < 0.001), cerebrovascular event (HR 2.80 [95% CI 1.14-6.86], p = 0.025) and acute respiratory distress syndrome (HR 3.50 [95% CI 1.63-7.51], p = 0.001) were identified as independent risk factors for the death of COVID-19. The median virus shedding period of survivors was 25 days, longer than the general population. CONCLUSIONS: Maintenance hemodialysis patients are a highly vulnerable population at increased risk of mortality and prolonged virus shedding period in the ongoing COVID-19 pandemic. Advanced age, decreased oxygen saturation, low DBP on admission, and complications like acute cardiac injury are parameters independently associated with poor prognosis.

MAD2B-mediated cell cycle reentry of podocytes is involved in the pathogenesis of FSGS.

Rationale: Focal segmental glomerulosclerosis (FSGS) is characterized by the dysfunction of "post-mitotic" podocytes. The reentry of podocytes in the cell cycle will ultimately result in cell death. Mitotic arrest deficient 2-like protein 2 (MAD2B), an inhibitor of anaphase-promoting complex (APC)/cyclosome, precisely controls the metaphase to anaphase transition and ordered cell cycle progression. However, the role of MAD2B in FSGS podocyte injury remains unknown. Methods: To explore MAD2B function in podocyte cell cycle reentry, we used conditional mutant mice lacking MAD2B selectively in podocytes in ADR-induced FSGS murine model. Additionally, KU-55933, a specific inhibitor of ataxia-telangiectasia mutated (ATM) was utilized in vivo and in vitro to explore the role of ATM in regulating MAD2B. Results: The expression of MAD2B in podocytes was dramatically increased in patients with FSGS and ADR-treated mice along with podocyte cell cycle reentry. Podocyte-specific knockout of MAD2B effectively attenuated proteinuria, podocyte injury, and prevented the aberrant cell cycle reentry. By bioinformatics analysis we revealed that ATM kinase is a key upstream regulator of MAD2B. Furthermore, inhibition of ATM kinase abolished MAD2B-driven cell cycle reentry and alleviated podocyte impairment in FSGS murine model. In vitro studies by site-directed mutagenesis and immunoprecipitation we revealed ATM phosphorylated MAD2B and consequently hampered the ubiquitination of MAD2B in a phosphorylation-dependent manner. Conclusions: ATM kinase-MAD2B axis importantly contributes to the cell cycle reentry of podocytes, which is a novel pathogenic mechanism of FSGS, and may shed light on the development of its therapeutic approaches.

The association of OPG polymorphisms with diabetic retinopathy in Chinese population.

PURPOSE: Genetic factors have been studied to be associated with diabetic retinopathy (DR). This study aimed to investigate the association between the polymorphisms in the osteoproterin (OPG) gene and DR in a Han Chinese population. METHODS: There were 475 patients with diabetic retinopathy (DR), 478 type 2 diabetes mellitus without retinopathy (DNR) and 469 healthy controls collected in this study. OPG single-nucleotide polymorphisms (SNPs) rs2073618 and rs3134069 were genotyped by Mass ARRAY MALDI-TOF system. The genotype and allele frequencies were evaluated using the χ2 tests. Odds ratio (OR) and 95% confidence intervals (95% CI) were calculated for the risk of genotype and allele. RESULTS: There was a statistically significant difference for OPG SNP rs3134069 between DR cases and healthy controls in the allelic model (P = .036, OR = 1.33, 95% CI = 1.02-1.73). The C allele frequency of this polymorphism was 0.154 in the DR cases, whereas it was 0.120 in healthy controls, suggesting a risk effect for DR. SNP rs3134069 had a significant association with DR in the dominant model (P = .038, OR = 1.37, 95% CI = 1.02-1.84), indicating that the CC/AC genotype was more likely to suffer from DR. For rs2073618, no significant difference was identified in the allelic model (P = .632, OR = 0.95, 95% CI = 0.78-1.16) and the four genetic models. CONCLUSIONS: This study showed that OPG SNP rs3134069 was associated with DR in the dominant model, suggesting that the OPG gene variant may be involved in the development of DR.

Relieving lipid accumulation through UCP1 suppresses the progression of acute kidney injury by promoting the AMPK/ULK1/autophagy pathway.

Rationale: Acute kidney injury (AKI) is a serious clinical emergency with an acute onset, rapid progression, and poor prognosis. Recent evidence suggests that AKI is accompanied by significant metabolic abnormalities, including alterations in lipid metabolism. However, the specific changes in lipids in AKI, and their role and regulation mechanisms are currently unclear. Methods: Quantitative metabolomics was performed in AKI models to reveal the differences of lipid metabolism-related products. Regulated pathway was detected by western blot, qRT-PCR, immunoblot analysis and immunohistochemistry. Results: The present study systematically analyzes the changes in lipid composition in AKI for the first time and find that the degree of lipid accumulation was highly correlated with uncoupling protein 1 (UCP1). Importantly, relieving lipid accumulation in AKI by upregulating UCP1 can significantly inhibit the progression of AKI through promoting AMPK/ULK1/autophagy pathway. Conclusions: The present findings suggest that lipid accumulation in AKI is directly regulated by UCP1, which can activate cell autophagy and thus significantly inhibit disease progression. It will provide new ideas and targets for the treatment of AKI.

MAD2B contributes to parietal epithelial cell activation and crescentic glomerulonephritis via Skp2.

Mitotic spindle assembly checkpoint protein 2 (MAD2B), a well-known anaphase-promoting complex/cyclosome (APC/C) inhibitor and a small subunit of DNA polymerase-ζ, is critical for mitotic control and DNA repair. Previously, we detected a strong increase of MAD2B in the glomeruli from patients with crescentic glomerulonephritis and anti-glomerular basement membrane (anti-GBM) rats, which predominantly originated from activated parietal epithelial cells (PECs). Consistently, in vitro MAD2B was increased in TNF-α-treated PECs, along with cell activation and proliferation, as well as extracellular matrix accumulation, which could be reversed by MAD2B genetic depletion. Furthermore, we found that expression of S phase kinase-associated protein 2 (Skp2), an APC/CCDH1 substrate, was increased in the glomeruli of anti-GBM rats, and TNF-α-stimulated PECs and could be suppressed by MAD2B depletion. Additionally, genetic deletion of Skp2 inhibited TNF-α-induced PEC activation and dysfunction. Finally, TNF-α blockade or glucocorticoid therapy administered to anti-GBM rats could ameliorate MAD2B and Skp2 accumulation as well as weaken PEC activation. Collectively, our data suggest that MAD2B has a pivotal role in the pathogenesis of glomerular PEC activation and crescent formation through induction of Skp2 expression.

Serologic Detection of SARS-CoV-2 Infections in Hemodialysis Centers: A Multicenter Retrospective Study in Wuhan, China.

RATIONALE & OBJECTIVE: Patients receiving maintenance hemodialysis (MHD) are highly vulnerable to infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The current study was designed to evaluate the prevalence of SARS-CoV-2 infection based on both nucleic acid testing (NAT) and antibody testing in Chinese patients receiving MHD. STUDY DESIGN: Cross-sectional study. SETTING & PARTICIPANTS: From December 1, 2019, to March 31, 2020, a total of 1,027 MHD patients in 5 large hemodialysis centers in Wuhan, China, were enrolled. Patients were screened for SARS-CoV-2 infection by symptoms and initial computed tomography (CT) of the chest. If patients developed symptoms after the initial screening was negative, repeat CT was performed. Patients suspected of being infected with SARS-CoV-2 were tested with 2 consecutive throat swabs for viral RNA. In mid-March 2020, antibody testing for SARS-CoV-2 was obtained for all MHD patients. EXPOSURE: NAT and antibody testing results for SARS-CoV-2. OUTCOMES: Morbidity, clinical features, and laboratory and radiologic findings. ANALYTICAL APPROACH: Differences between groups were examined using t test or Mann-Whitney U test, comparing those not infected with those infected and comparing those with infection detected using NAT with those with infection detected by positive serology test results. RESULTS: Among 1,027 patients receiving MHD, 99 were identified as having SARS-CoV-2 infection, for a prevalence of 9.6%. Among the 99 cases, 52 (53%) were initially diagnosed with SARS-CoV-2 infection by positive NAT; 47 (47%) were identified later by positive immunoglobulin G (IgG) or IgM antibodies against SARS-CoV-2. There was a spectrum of antibody profiles in these 47 patients: IgM antibodies in 5 (11%), IgG antibodies in 35 (74%), and both IgM and IgG antibodies in 7 (15%). Of the 99 cases, 51% were asymptomatic during the epidemic; 61% had ground-glass or patchy opacities on CT of the chest compared with 11.6% among uninfected patients (P<0.001). Patients with hypertensive kidney disease were more often found to have SARS-CoV-2 infection and were more likely to be symptomatic than patients with another primary cause of kidney failure. LIMITATIONS: Possible false-positive and false-negative results for both NAT and antibody testing; possible lack of generalizability to other dialysis populations. CONCLUSIONS: Half the SARS-CoV-2 infections in patients receiving MHD were subclinical and were not identified by universal CT of the chest and selective NAT. Serologic testing may help evaluate the overall prevalence and understand the diversity of clinical courses among patients receiving MHD who are infected with SARS-CoV-2.

Selenoprotein T protects against cisplatin-induced acute kidney injury through suppression of oxidative stress and apoptosis.

Previously, selenoprotein T (SelT) expression was shown to be induced in nervous, endocrine, and metabolic tissues during ontogenetic and regenerative processes. However, whether SelT plays a critical role in renal diseases remains unclear. Here, we explored the role of SelT in cisplatin-induced acute kidney injury (AKI). Results revealed that SelT was highly expressed in renal tubules, but its expression was significantly reduced in cisplatin-induced AKI. Importantly, knocking down of SelT expression in kidney cells in vitro resulted in cisplatin-induced cell apoptosis, as indicated by the elevation of cleaved-PARP and Bax expression, Caspase-3 activity, and number of TUNEL-positive cells. Moreover, SelT silencing-induced reactive oxygen species (ROS) production, accompanied by a decrease in intracellular superoxide dismutase (SOD) and catalase (CAT) activity and increase in malondialdehyde (MDA) content. Notably, the protein and mRNA levels of Nox4 were increased in response to SelT downregulation. Furthermore, suppression of Nox4 expression by GKT137831 partially alleviated SelT knockdown-induced ROS generation and cell apoptosis in cisplatin-treated kidney cells. Taken together, our findings provide the first evidence that SelT protects against cisplatin-induced AKI by suppression of oxidative stress and apoptosis.

Clinical Characteristics of and Medical Interventions for COVID-19 in Hemodialysis Patients in Wuhan, China.

BACKGROUND: Reports indicate that those most vulnerable to developing severe coronavirus disease 2019 (COVID-19) are older adults and those with underlying illnesses, such as diabetes mellitus, hypertension, or cardiovascular disease, which are common comorbidities among patients undergoing maintenance hemodialysis. However, there is limited information about the clinical characteristics of hemodialysis patients with COVID-19 or about interventions to control COVID-19 in hemodialysis centers. METHODS: We collected data retrospectively through an online registration system that includes all patients receiving maintenance hemodialysis at 65 centers in Wuhan, China. We reviewed epidemiologic and clinical data of patients with laboratory-confirmed COVID-19 between January 1, 2020 and March 10, 2020. RESULTS: Of 7154 patients undergoing hemodialysis, 154 had laboratory-confirmed COVID-19. The mean age of the 131 patients in our analysis was 63.2 years; 57.3% were men. Many had underlying comorbidities, with cardiovascular disease (including hypertension) being the most common (68.7%). Only 51.9% of patients manifested fever; 21.4% of infected patients were asymptomatic. The most common finding on chest computed tomography (CT) was ground-grass or patchy opacity (82.1%). After initiating comprehensive interventions-including entrance screening of body temperature and symptoms, universal chest CT and blood tests, and other measures-new patients presenting with COVID-19 peaked at 10 per day on January 30, decreasing to 4 per day on February 11. No new cases occurred between February 26 and March 10, 2020. CONCLUSIONS: We found that patients receiving maintenance hemodialysis were susceptible to COVID-19 and that hemodialysis centers were high-risk settings during the epidemic. Increasing prevention efforts, instituting universal screening, and isolating patients with COVID-19 and directing them to designated hemodialysis centers were effective in preventing the spread of COVID-19 in hemodialysis centers.

Subcellular trafficking of tubular MDM2 implicates in acute kidney injury to chronic kidney disease transition during multiple low-dose cisplatin exposure.

Acute kidney injury (AKI) is the leading cause of renal failure, and quite a few patients will advance to chronic kidney disease (CKD) in the long term. Here, we explore the roles and mechanisms of tubular epithelial cells (TECs) during repeated cisplatin (CP) induced AKI to CKD transition (AKI-CKD). Previously, we reported that murine double minute 2 (MDM2), an E3-ubiquitin ligase, is involved in tubulointerstitial fibrosis. However, whether tubular MDM2 is implicated in AKI-CKD is undefined. Currently, we confirmed that during AKI-CKD, MDM2 shifts from nucleus to cell membrane in TECs both in vivo and in vitro. Whereas regulating MDM2 distribution chemically or genetically has a prominent impact on tubular disorders. And then we investigated the mechanisms of the above findings. First, in the nucleus, repeated CP administration leads to MDM2 reduction with escalated p53 and cell cycle G2/M arrest. On the other hand, multiple CP treatment increases the level of membranous MDM2 with ensuing integrin ß8 degradation and TGF-ß1 activation. More interestingly, anchoring MDM2 on cell membranes can mimic the reduction of integrin ß8 arousing by repeated CP exposure. Collectively, our findings provided the evidence that tubular MDM2 subcellular shuttling is involved in AKI-CKD through p53-G2/M arrest and integrin ß8 mediated TGF-ß1 activation.

Rhodojaponin II attenuates kidney injury by regulating TGF-ß1/Smad pathway in mice with adriamycin nephropathy.

ETHNOPHARMACOLOGICAL RELEVANCE: Rhododendron molle G. Don (Ericaceae) (RM) is a natural medicinal plant. Its root extracts have been applied in clinic and proved to be effective in chronic glomerulonephritis and rheumatoid arthritis in China. Surprising, little is understood about the key compound of RM and the exact mechanisms underlying its treatment on kidney diseases. In this study, we will explore whether rhodojaponin II (R-II), as the important compound of RM, also exerts the major effect. MATERIALS AND METHODS: Mouse model of focal segmental glomerulosclerosis was induced by single dose of adriamycin injection. Induced adriamycin nephropathy (ADRN) mice were treated individually with RM root extract (5 mg/kg, n = 5), RM root extract (60 mg/kg, n = 5), R-II (0.04 mg/kg, n = 6) or captopril (30 mg/kg, n = 5) for five weeks. Podocyte marker (nephrin and podocin) expressions were examined by immunohistochemical staining and Western Blot analysis. Fibronectin level was evaluated by immunohistochemical staining and Western Blot analysis. Interstitial infiltrated inflammatory cells (CD4+ T cells, CD8+ T cells, and CD68+ macrophages) were examined with immunohistochemical staining. The expressions of NF-ĸB p-p65 and TGF-ß1/Smad pathway associated key proteins, such as TGF-ß1, Smad3, phosphorylated-Smad3 (p-Smad3), and Smad7, were analyzed respectively by Western Blot analysis. RESULTS: RM root extract (5 mg/kg) and its important compound R-II (0.04 mg/kg) significantly ameliorated proteinuria, podocyte injury, and glomerulosclerosis, meanwhile, they hampered interstitial fibrosis in mice with ADRN. R-II significantly reduced NF-ĸB p65 phosphorylation, interstitial infiltrated CD4+ T cells, CD8+ T cells, and CD68+ macrophages, at the same time, down-regulated TGF-ß1 and p-Smad3 protein expressions in mice with ADRN. CONCLUSION: RM root extract, R-II, could effectively ameliorate proteinuria and kidney injury in ADRN, related to its anti-inflammatory effects, as well as suppression of TGF-ß1/Smad signaling pathway.

Inhibition of SIRT2 Alleviates Fibroblast Activation and Renal Tubulointerstitial Fibrosis via MDM2.

BACKGROUND/AIMS: Renal tubular epithelial cells and fibroblasts are the main sources of myofibroblasts, and these cells produce the extracellular matrix during tubulointerstitial fibrosis (TIF). Histone deacetylases (HDAC) inhibitors exert an antifibrogenic effect in the skin, liver and lung. Sirtuin 2 (SIRT2), which is a class III HDAC, is an important member of NAD+-dependent protein deacetylases. The current study evaluated the role of SIRT2 in renal TIF. METHODS: Immunohistochemical staining and Western blot were performed to evaluate SIRT2 expression in TIF patients and unilateral urethral obstruction (UUO) mice. Western blot was used to assess the protein levels of SIRT2, α-SMA, collagen III, fibronectin, and MDM2 in tubular epithelial cells and fibroblasts. The specific inhibitor AGK2 was used to inhibit SIRT2 activity, and targeted siRNA was used to suppress SIRT2 expression. RESULTS: SIRT2 expression increased in the tubulointerstitium of TIF patients and UUO mice. SIRT2 inhibition ameliorated TIF in UUO mice. SIRT2 expression in tubular cells was unchanged after exposure to TGF-ß1. The SIRT2-specifc inhibitor AGK2 did not attenuate TGF-ß1-induced tubular epithelial-mesenchymal transition. However, SIRT2 was upregulated in fibroblasts, and fibroblasts were activated after TGF-ß1 treatment. Genetic knockdown and chemical inhibition of SIRT2 attenuated TGF-ß1-induced fibroblast activation. We also explored the downstream signaling of SIRT2 during fibroblast activation. Genetic knockdown and chemical inhibition of SIRT2 suppressed TGF-ß1-induced increase in MDM2 expression, and inhibition of the MDM2-p53 interaction using Nutlin-3 did not suppress SIRT2 upregulation. CONCLUSION: Our results suggest that SIRT2 participates in the activation of fibroblasts and TIF, which is mediated via regulation of the MDM2 pathway, and the downregulation of SIRT2 may be a therapeutic strategy for renal fibrosis.